1. Field of the Invention
The present invention relates to a photosensitive composition used as a resist material.
2. Description of the Related Art
Photoresists are used widely in the field of electronic components requiring various micropatterning operations, as in the field of semiconductors integrated circuits such as LSIs. In particular, in order to achieve a high degree of integration along with developments of multifunctional, and high-density electronic devices, forming fine resist patterns has been required. As one method for forming a fine resist pattern, a radiation source for emitting light having a short wavelength is used. For example, it has been attempted to use a KrF excimer laser (wavelength: 248 nm) as a radiation source or to apply exposure to an ionizing radiation such as an electron beam or X-ray so as to form a fine resist pattern. Accordingly, strong demand has arisen for developing a resist material having a high sensitivity and a high resolution in the case of applying the above light source and a high resistance to etching for forming a fine pattern.
A so-called chemical amplification type resist is disclosed in Published Unexamined Japanese Patent Application No. 63-27829 as a resist material having a high sensitivity for the excimer laser, an ultraviolet ray having a short wavelength, and the ionic radiation and a sufficiently high resistance to dry etching for forming a fine pattern. This chemical amplification type resist is a composition containing an alkali-soluble resin, a dissolution inhibitor, and an arylonium salt as an acid generator. The dissolution inhibitor in this composition reduces solubility of the alkali-soluble resin in the alkaline solution at a nonexposed portion, and the arylonium salt generates an acid at an exposed portion. In addition, baking is performed to cause the acid to decompose the dissolution inhibitor, and only the exposed portion is dissolved in an alkaline solution (i.e., a developing solution), thus obtaining a positive resist pattern. In the resist containing the acid generator, however, when the content of the acid generator is excessive, or the baking temperature performed upon exposure is excessively high, or the baking time is excessively long, this resist does not serve as a high-sensitivity positive resist material. In this composition, the acid generated from the acid generator quickly loses its activity during a period from the end of exposure to the start of baking. For this reason, this composition cannot be stable resist during process for forming a resist pattern.